The disadvantages of conventional waste water treatment systems is recognized in U.S. Pat. No. 5,618,414 to Goupil, et al. As described in Goupil, et al., conventional means for treating waste water collected in septic tank systems include treatment in a mechanically aerated treatment plant, which has high operational costs. Other waste water treatment systems in the art include soil and sand absorption systems. The disadvantages of these latter systems include the requirement of large surface areas of land. Moreover, conventional soil and sand absorption systems are not conducive in soils with high ground water tables or with low permeability characteristics.
The waste water treatment system described in Goupil et al. employs a pretreatment biofilter which collects wastewater from a septic system and removes metal and microbial contaminants from the effluent prior to dispersal to an absorption field. The biofilter in Goupil et al. also employs peat as the filtering media, peat having been long recognized in the waste water treatment art as being effective in removing pollutants and microbial activity. In Goupil, the peat is contained within two separate treatment chambers, and wastewater influent is distributed over the peat filtering media via a distribution plate. The embodiments taught in Goupil et al. are designed for use in an absorption field where the treated effluent is dispersed through the floor of the biofilter.
The present invention is directed to an improved biofilter that, in certain aspects, is especially conducive for use in drip irrigation applications wherein the biofilter comprises a water-tight container that prevents wastewater effluent from leaking out of the biofilter into the surrounding environment. In other aspects of the invention, the biofilter comprises an improved filtering composition comprising peat and coconut fibers that are contained within a plurality of sacks layered upon one another within the biofilter.
Specifically, the inventive biofilter comprises, in certain embodiments, (a) a container having an interior, an upper end, and a lower floor having a plurality of apertures through which wastewater effluent may flow; (b) a plurality of sacks housed within the interior of the container, wherein each of the sacks is formed of a porous material; and (c) a composition of filtering material contained within each of the sacks. Preferred compositions of filtering material include peat (preferably 80-85%), coconut fibers (preferably 10-20%), large cell, fixed film media blocks formed of, for example, rigid PVC (preferably up to 5%), and sand. The biofilter further includes a wastewater inlet disposed near the upper end of the container which is in communication with the interior of the container for receiving wastewater carried therein for treatment. The wastewater inlet is disposed such that the wastewater influent within the container flows downward via gravity through the sacks and exits the biofilter through the floor apertures. This embodiment is designed for subsurface installations where dispersal of the treated effluent into the underlying ground is desired.
The present invention is also directed to a biofilter design conducive for use in high water areas where effluent is disposed via drip irrigation or any absorption field. Specifically, the biofilter comprises a container having an interior, an upper end, side walls, and a solid, aperture-free lower floor integral with the side walls. This design results in a water-tight, leak-proof container which prevents contamination of the underlying ground with wastewater effluent. This embodiment of the inventive biofilter further includes a plurality of sacks housed within the interior of the container, wherein each of the sacks is formed of a porous material. Contained within each sack is a filtering composition preferably comprising peat, coconut fibers, large cell, fixed film media blocks (as described above), and sand. This embodiment further includes a wastewater inlet disposed near the upper end of the container which is in communication with the interior of the container for receiving wastewater influent carried into the container from a septic tank for treatment therein. The wastewater inlet is disposed such that the wastewater influent within the container flows downward via gravity through the sacks. Disposed near the lower floor is a wastewater outlet and a conduit connected to and extending from the container. The conduit is in communication with the wastewater outlet at one end and connected to, and extending from, a pump tank at another end of the conduit. The conduit is further configured to carry treated wastewater effluent from the container through the wastewater outlet via the pump for final discharge into the drip lines.
In both embodiments, the biofilter may include a layer of brick chips or lika rock on the floor for aiding in the removal of certain contaminants and nutrients as well as for providing added weight to the biofilter. Also, a second composition of filtering material is preferably placed within the interior of the container and disposed loosely therein to fill the interstitial spaces between the layered sacks. Preferably, this second composition of filtering material is the same as that contained within the sacks. The employment of individual sacks for housing the filtering composition is beneficial in terms of improved filtering efficiency, especially if the sacks are layered upon one another in opposite directions within the biofilter container. By utilizing individual sacks, the filtering material contained therein is more evenly dispersed, compared to a loose fill biofilter where voids may result within the biofilter such that some wastewater effluent may exit the biofilter untreated. Moreover, the employment of the individual sacks provides for improved maintenance, since it is easier to install and to remove individual sacks when replacing the interior of the biofilter as opposed to a loose fill of filtering material.
The present invention is also directed to a biofilter for treating wastewater wherein instead of using a peat-containing filtering media, course sand is employed. In this embodiment, the biofilter acts as a re-circulating sand filter. Specifically, the biofilter comprises a water-tight, leak-proof container having an interior, an upper end, side walls, and a solid, aperture-free lower floor integral with the side walls. Disposed within the interior is a sufficient amount of sand to fill at least 50%, and more preferably at least 90%, of the container""s interior. The biofilter further comprises a wastewater inlet disposed near the upper end of the container that is in communication with the interior for receiving wastewater influent from a septic tank, the inlet being disposed such that the influent flows downward through the sand for treatment. A wastewater outlet is disposed near the lower floor of the container, and a conduit is connected to, and extends from, the container, the conduit being in communication with the outlet at one end and connected to a pump at another end. The pump removes the treated effluent from the biofilter.
The present invention provides an improved method of treating wastewater that is more efficient and provides for a cleaner effluent, thereby allowing the construction of larger buildings on smaller lots, wherein septic tanks are employed. The present invention is also more user-friendly in that it is smaller, easier to install than other types of biofilters, as well as easier to maintain than conventional biofilters.